1. Field of the Invention
The present invention relates to an image reader which can edit a plurality of images.
2. Description of the Prior Art
An image reader detects an image on a document with an image sensor, binarizes the obtained signal of the detected image with a predetermined processing method such as a bi-level or dither processing so as to transform the signal into binary image signal data, and sends the binarized signal data to an output apparatus such as a printer.
It is desirable to binarize signal data of an image with use of a predetermined threshold level (bi-level processing) if it includes only characters and/or line figures. And, if it includes an image of half-tone therein, it is desirable to binarize signal data with use of a halftone processing such as a dither matrix.
On the binarization of an image wherein characters and a half-tone image coexist at the same time, it is necessary to assign the bi-level and dither processings to each part of the image.
It is also desirable for an image reader to have editorial functions such as masking, trimming and reversal of image between black and white, besides a switching function for switching the bi-level processing to dither processing or vice versa according to the property of image.
In an image processor disclosed in Japanese Patent Laid Open Publication No. 45,765/1984, a signal for designating the bi-level or dither processing is allotted to each small area defined on a document, and it is stored in a zone memory. Then, image data of each small area are stored in either an image memory provided for bi-level processing or another for dither processing according to the designation of individual signal stored in the zone memory. Next, the image data read from both image memories are binarized wih a bi-level processing, if it is designated by said signal, and with a dither-processing, if it is designated, respectively, and the binarized signals are sent to the same image output apparatus.
However, in the image processor of this type, image memories, each having a large capacity for example of a full memory for A3 size, are needed besides the zone memory.